The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2002-312387 filed Oct. 28, 2002.
1. Field of the Invention
The present invention relates to a lens barrel capable of correcting a blur occurring in a subject image, which is used in an optical apparatus such as a camera.
2. Description of Related Art
Blur correction systems in the related art include a system that moves a blur correction optical system in a direction substantially perpendicular to an optical axis with an actuator, such as a voice coil motor (VCM).
For instance, a blur correction device disclosed in Japanese Laid-Open Patent Publication No. 11-271833 comprises a locking device that holds a blur correction optical system at a specific position, that is, locks the blur correction optical system while it is not engaged in blur correcting operation.
FIGS. 6 and 7 show sectional view of part of a lens barrel having a blur correction device in the related art.
When performing blur correction, electric current is supplied to a coil 20 to move a blur correction lens L and control its position in two directions perpendicular to an optical axis O and also perpendicular to each other. The blur correction lens L needs to be kept at a fixed position while blur correction is not performed. However, a great deal of power will be consumed if power is always supplied to the coil 20 to keep the position of the blur correction lens L.
When image blur in an image plane is unlikely to occur and blur correction is not being performed, there is no need to move a lens holding frame 10. In this case, the lens holding frame 10 and the blur correction lens L are locked by moving a lock pin 70b in a direction of the optical axis O to be inserted into a hole 10b, as shown in FIG. 6.
With the lens barrel in the related art, the locking operation is executed when an optical axis OL of the blur correction lens L and the optical axis O of a photographic optical system have matched with each other. In addition, the internal diameter of the hole 10b is set larger than the outside diameter of the lock pin 70b so that the lock pin 70b is inserted in the hole 10b with a high degree of reliability.
After the lock pin 70b is inserted into the hole 10b, power supply to the coil 20 is cut off, and thus locking operation is completed.
FIG. 7 shows the lens barrel shown in FIG. 6, which is in a state where the lock pin 70b and the hole 10b are engaged with each other and power supply to the coil 20 has stopped.
The lens holding frame 10 falls in a direction of gravity (a direction of arrow G shown in FIG. 7) under its own weight upon stopping of power supply to the coil 20. The lens holding frame 10 will no longer fall after the lock pin 70b and the hole 10b come into contact with each other, as shown in FIG. 7.
However, if power supply to the coil 20 has stopped and the lens holding frame 10 has fallen by its own weight, the optical axis OL of the blur correction lens L shifts from the optical axis O of the photographic optical system so that they become eccentric. There is a problem in that the optical performance of the photographic optical system slightly deteriorates when the optical axis OL of the blur correction lens L and the optical axis O of the photographic optical system do not match with each other.
The present invention is to provide a lens barrel having blur correction function, allowing the photographic optical system to work as effective as possible while blur correction is not performed.
A lens barrel according to the present invention, comprises: a main optical system; a blur correction optical system included in the main optical system, that corrects image blur by moving along directions intersecting an optical axis of the main optical system; a lens holding frame that holds the blur correction optical system and is allowed to move along the directions intersecting the optical, axis of the main optical system; a blur correction drive unit that drives the blur correction optical system and the lens holding frame; and a lock mechanism that restricts movement of the blur correction optical system and the lens holding frame, leaving a play, when blur correction is not executed; wherein: the lock mechanism comprise a frame engaging portion provided at the lens holding frame and a movable engaging portion that moves substantially along the optical axis of the main optical system and is capable of engaging with the frame engaging portion; an optical axis of the blur correction optical system matches the optical axis of the main optical system when the movable engaging portion and the frame engaging portion are in contact with each other, after the movable engaging portion moves to a position to engage with the frame engaging portion and the blur correction optical system and the lens holding frame move in a predetermined direction by the play.
It is preferable that the predetermined direction corresponds to a direction from the optical axes to a bottom portion of a camera body at which the lens barrel has been mounted.
A lens barrel according to the present invention, comprises: a main optical system; a blur correction optical system included in the main optical system, that corrects image blur by moving along directions intersecting an optical axis of the main optical system; a lens holding frame that holds the blur correction optical system and is allowed to move along the directions intersecting the optical axis of the main optical system; a blur correction drive unit that drives the blur correction optical system and the lens holding frame; a lock mechanism that restricts movement of the blur correction optical system and the lens holding frame when blur correction is not executed, the lock mechanism comprising a frame engaging portion provided at the lens holding frame and a movable engaging portion that moves substantially along the optical axis of the main optical system and is capable of engaging with the frame engaging portion; and a biasing device that applies force to the lens holding frame and the blur correction optical system along a direction intersecting with the optical axis of the main optical system when the movable engaging portion has moved to a position to engage with the frame engaging portion.
It is preferable that an optical axis of the blur correction optical system and the optical axis of the main optical system match when the movable engaging portion and the frame engaging portion are caused to be in contact with each other by the biasing device. It is preferable that the biasing device is the blur correction drive unit.
It is preferable that the direction along which the biasing device applies the force to the lens holding frame and the blur correction optical system corresponds to a direction from the optical axes to a bottom portion of a camera body at which the lens barrel has been mounted. It is preferable that the main optical system is a photographic optical system that forms an image of a subject to be photographed; and the biasing device starts applying the force to the lens holding frame and the blur correction optical system immediately before photographing and continues applying the force at least while photographing.
The frame engaging portion may be a hole provided in the lens holding frame, facing substantially along the optical axis of the main optical system; and the movable engaging portion may be a lock pin capable of being inserted into the hole.
A camera system according to the present invention comprises a camera body and a lens barrel as described above.